LIGHT GUIDE SET, ILLUMINATION DEVICE AND DISPLAY DEVICE
In order for a light guide set including a light source such as an LED and a light guide member receiving light without leakage of light from the light source or the like to be provided, in the light guide set (ST) that includes an LED (32) and an light guide bar (11) which includes a light reception end (12R) receiving light from the LED (32) and which guides the received light and a holding member (25) which holds the LED (32) and the light reception end (12R) thereof on the side of the LED (32), a protrusion (11P) (a second engagement portion/a first engagement portion) is formed in the light guide bar (11), and an opening hole (26Dh) (the first engagement portion/the second engagement portion) is formed in the holding member (25).
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The present invention relates to a light guide set including at least a light source and a light guide bar for guiding light, an illumination device incorporating a light guide set and a display device incorporating an illumination device.
BACKGROUND ARTIn general, a liquid crystal display device (display device) incorporating a non-light emission liquid crystal display panel (display panel) includes a backlight unit (illumination device) that supplies light to the liquid crystal display panel. The backlight unit preferably generates planar light that spreads over the entire region of the planar liquid crystal display panel. Hence, the backlight unit may include a light guide member for mixing, to a high degree, the light of a light source (for example, a light emitting element such as an LED) incorporated.
For example, in the backlight unit of patent document 1, as shown in
- Patent document 1: JP-A-2007-227074
Incidentally, the light guide bars 111 and the LEDs 132 are not connected directly or indirectly. Specifically, part of the frame 142A parallel to the bottom surface 142B of the backlight chassis 142 only presses LED modules mj and the light guide bars 111. Hence, the LEDs 132 are likely to be displaced with respect to the light guide bars 111. If such an event occurs, it is likely that light from the LEDs 132 sufficiently does not enter the light guide bars 111.
The present invention is made in view of the foregoing conditions. An object of the present invention is to provide a light guide set or the like that includes a light source such as an LED and a light guide bar which receives light from the light source without leakage of the light.
Means for Solving the ProblemA light guide set includes: a light source; a light guide bar that includes a light reception end receiving light from the light source and that guides the received light; and a holding member that holds the light source and a side of the light reception end of the light guide bar. In the light guide set described above, among a first engagement portion and a second engagement portion that engage with each other, one of the engagement portions is formed in the light guide bar, and the other engagement portion is formed in the holding member.
In this configuration, the holding member simultaneously holds (retains) the light source and the light guide bar. Moreover, through the engagement portions, the light guide bar is stably fixed to the holding member. Hence, the light of the light source reliably enters the light guide bar through the light reception end. Consequently, the light guide set guides the light of the light source without leakage.
Preferably, the first engagement portion and the second engagement portion are also fitting portions that fit each other, and one of the engagement portions is convex, and the other engagement portion is so concave as to fit the convex engagement portion. In this configuration, the degree of the engagement is reliably enhanced.
Preferably, the holding member has a hollow, and the light source and a part of the light guide bar are held within the hollow. In this configuration, the light source and the light guide bar are in contact with the inner wall surface of the hollow of the holding member and thus are prevented from moving, with the result that the light of the light source reliably enters the light guide bar through the light reception end.
Preferably, the first engagement portion and the second engagement portion engage with each other such that the light reception end is separated from the light source placed at an end of the hollow of the holding member. In this configuration, the light guide bar and the light source are not in contact with each other, and thus they are prevented from being damaged.
Preferably, the holding member is an aggregation of a plurality of holding member parts, and the light source and the light guide bar are held in the holding member by being sandwiched between the holding member parts. In this configuration, the assembly of the light guide set is facilitated.
A clip that retains the light guide bar may be included. With this clip, when the light guide set is incorporated in, for example, the chassis of the illumination device, if the clip and the chassis engage with each other, the clip achieves the function of supporting the light guide bar.
Preferably, when the light guide bar includes: a light propagation portion that propagates the received light by reflecting the received light multiple times therewithin; and a light emission portion that emits the propagated light to the outside, the clip retains the propagation portion or the light emission portion.
Preferably, when a plurality of the light guide bars are provided, the light guide bars are coupled to each other through a coupling member. In this configuration, for example, when the group (light guide bar group) in which the light guide bars are continuously arranged is formed, it is possible to carry the light guide bar group (in short, it is possible to carry a large number of light guide bars at one time). Hence, the handling of the light guide bars is facilitated.
A clip that retains the coupling member may be included. Preferably, a part member along a direction in which the light guide bars extend is connected to the coupling member, and the clip catches the part member.
In this configuration, for example, even if the light guide bar is extended by the heat of the light source or other circuit components, the clip reliably catches the part member, and hence stably retains the light guide bar.
Preferably, in order to facilitate the handling, when a plurality of the light guide bars are provided, the holding members are integrally continuous.
An illumination device including: the light guide set described above; and a chassis that holds the light guide set is also said to be according to the present invention. An illumination device including: a diffusion plate that is supported by the surface of the holding member and that receives light from the light guide set; and an optical member that is supported by the diffusion plate and that transmits light from the diffusion plate is also said to be according to the present invention.
Preferably, in the illumination device, the holding member engages with the chassis and the clip also engages with the chassis such that the light guide bar is prevented from moving with respect to the chassis.
A display device including: the illumination device described above; and a display panel that receives light from the illumination device is also said to be according to the present invention.
Advantages of the InventionAccording to the present invention, since the positional relationship between the light source and the light guide bar is not changed, the light guide bar receives light without leakage of the light of the light source.
An embodiment will be described below with reference to accompanying drawings. For convenience, member symbols and the like may be omitted; in that case, other drawings should be referenced. For convenience, a drawing other than a cross-sectional view may be hatched. A black dot shown together with arrows means a direction perpendicular to the plane of the figure.
As shown in
In the liquid crystal display panel 59, an active matrix substrate 51 including switching elements such as TFTs (thin film transistors) and an opposite substrate 52 opposite the active matrix substrate 51 are adhered with a sealant (not shown). Liquid crystal (not shown) is injected into a gap between both the substrates 51 and 52.
Polarization films 53 are attached to the light reception surface side of the active matrix substrate 51 and the emission side of the opposite substrate 52. The liquid crystal display panel 59 described above utilizes variations in transmittance caused by the inclination of liquid crystal molecules, and displays an image.
The backlight unit 49 arranged directly below the liquid crystal display panel 59 will now be described. The backlight unit 49 includes LED modules (light source modules) MJ, light guide bars (light guide members) 11, a support stage 21, a holding member 25, a reflective sheet 41, a backlight chassis 42, a diffusion plate 43, a prism sheet 44 and a lens sheet 45.
The LED module MJ is a module that emits light, and includes a mounting substrate 31, and an LED (light emitting diode) 32 mounted on the substrate surface of the mounting substrate 31.
The mounting substrate 31 is a plate-shaped and rectangular substrate; on the mounting surface 31U, a plurality of electrodes (not shown) are arranged. The LEDs 32 are attached onto the electrodes described above. The backlight unit 49 includes two mounting substrates 31; the mounting substrates 31 are arranged such that the mounting surfaces 31U are opposite each other (a direction in which the mounting substrate 31 extends is referred to as an X-direction, a direction in which the two mounting substrates 31 are aligned is referred to as a Y-direction and a direction intersecting the X-direction and the Y-direction is referred to as a Z-direction).
The LED 32 is mounted on the electrodes (not shown) formed on the mounting surface of the mounting substrate 31, and thereby receives the supply of current to emit light. In order for a sufficient amount of light to be ensured, a plurality of LEDs (light emitting elements; point light sources) are preferably mounted on the mounting substrate 31. For convenience, in the figure, part of the LEDs 32 is only shown.
The light guide bar 11 is a bar-shaped member that is made of transparent resin such as acryl resin or polycarbonate, and receives light from the LED 32 to guide the light therewithin (to perform light guidance). Specifically, as shown in
In the light guide bar 11, an end in the total length direction is referred to as a light reception end 12R that receives the light from the LED 32, and the other end in the total length direction, that is, the end on the opposite side of the light reception end 12R is referred to as a top end 12T (the area (the perimeter surrounding the light emission surface of the LED 32) of the LED 32 supplying light to the light reception end 12R of the light guide bar 11 is less than the area of the light reception end 12R). As shown in
Furthermore, the light guide bar 11 includes a processing portion 13 that changes the light propagating therewithin into an optical path suitable for emission to the outside (in short, an optical path is changed such that the light can be emitted through the side surface 12S of the light guide bar 11 without being totally reflected). This processing portion (optical path change processing portion) 13 is a surface in which, in the side of the top end 12T of the light guide bar 11, for example, as shown in
However, the processing portion 13 is not limited to the prism processing portion 13 where the triangular prisms 13PR are arranged close to each other; the processing portion 13 may be either a portion that is subjected to graining processing or a portion that is subjected to dot-type printing processing (the processed surface is parallel to an arrangement plane direction in which a plurality of light guide bars 11 (a direction of an X-Y plane specified by the X-direction and the Y-direction) are aligned.
The portion that is subjected to the prism processing and the portion that is subjected to the graining processing reflect or refract and transmit the light and thereby change the direction of travel of the light, and prevent the side surface 12S of the light guide bar 11 from totally reflecting the light, with the result that the light is emitted to the outside. The portion that is subjected to dot-type printing processing is formed of, for example, white ink, and diffuses or reflects the light and thereby changes the direction of travel of the light, and prevents the side surface 12S of the light guide bar 11 from totally reflecting the light, with the result that the light is emitted to the outside (a portion of the light propagation portion 12 that includes the processing portion 13 and that covers the processing portion 13 is referred to as a light emission portion 12N).
As shown in
In the light guide bar group GR, in which, as described above, the light guide bars 11 guiding the light from the LEDs 32 are collected, a plurality of light guide bars 11 are arranged as shown in
The light guide bar groups GR aligned along one of the mounting substrates 31 and the light guide bar groups GR aligned along the other mounting substrate 31 are symmetric with respect to a line. In the following description, a collection of the light guide bar groups GR is referred to as a light guide unit UT (the number of light guide bar groups GR included in the light guide unit UT is not limited to two or more; the number can be one).
The support stage 21 is a stage that supports the LED modules MJ. The support stage 21 includes a side wall 21S that supports the non-mounting surface 31B (the back surface of the mounting surface 31U) of the mounting substrate 31 and a bottom wall 21B that is connected to the side wall 21S and that is fixed to the bottom surface 42B of the backlight chassis 42 (the fixing method is not particularly limited).
Specifically, the side wall 21S and the bottom wall 21B are continuous so as to form the shape of a letter L as seen from a cross section (an Y-Z plane direction) perpendicular to the longitudinal direction of the mounting substrate 31. Hence, when the bottom wall 21B of the support stage 21 is fixed to the bottom surface 42B of the backlight chassis 42, the side wall 21S rises with respect to the bottom surface 42B of the backlight chassis 42. Then, when the side wall 21S makes intimate contact with the non-mounting surface 31B of the mounting substrate 31 and supports it, the LEDs 32 on the mounting surface 31U can make the light travel along a direction within the plane of the backlight chassis 42 (X-Y plane direction).
The holding member 25 holds not only the LEDs 32 but also the side of the light reception end 12R of the light guide bar 11 (a collection of the LEDs 32, the light guide bars 11 and the holding member 25 is referred to as a light guide set ST). The holding member 25 may be a division-type, that is, may be formed with two members; for example, a first holding member part 26 and a second holding member part 27 are combined together to complete the holding member 25 (in short, an aggregation of the holding member parts 26 and 27 is the holding member). The holding member 25 will be described in detail later.
The reflective sheet 41 is a sheet that is covered by the bottom surfaces 12B (each of which is one surface of the four side surfaces 11S of the light guide bar 11) of a plurality of light guide bars 11; the reflective surface 41U of the sheet faces the bottom surfaces 12B of the light guide bars 11. When there is light that leaks from the bottom surfaces 12B of the light guide bars 11, the reflective sheet 41 reflects the light to return it to the light guide bars 11, and thus loss of the light is prevented (for convenience, in various drawings, the reflective sheet 41 may be omitted).
As shown in
The diffusion plate 43 is a plate-shaped optical member that covers the light guide units UT, and diffuses light emitted from the light guide units UT. Specifically, the diffusion plate 43 diffuses the planar light (in short, the light from the light guide units UT) formed by overlapping light from a plurality of light guide bars 11, and spreads the light over the entire region of the liquid crystal display panel 59 (the diffusion plate 43 may be placed between the surfaces (in particular, the pressing member 27M of the second holding member part 27, which will be described later) of the holding members 25 arranged opposite each other.
The prism sheet 44 is a sheet-shaped optical member that covers the diffusion plate 43. In the prism sheet 44, for example, triangular prisms extending in one direction (linearly) are aligned, within the sheet surface, in a direction intersecting the one direction. Thus, the prism sheet 44 changes the radiation characteristic of the light from the diffusion plate 43.
The lens sheet 45 is a sheet-shaped optical member that covers the prism sheet 44. In the lens sheet 45, minute particles for refracting and scattering light are dispersed therewithin. In this way, the lens sheet 45 prevents the light from the prism sheet 44 from being locally collected, and thereby reduces the contrast (variations in the amount of light).
In the backlight unit 49 described above, the light from a plurality of LED modules MJ is changed into the planar light by the light guide unit UT, and the planar light is transmitted through a plurality of optical members 43 to 45, and is supplied to the liquid crystal display panel 59. In this way, the non-light emission liquid crystal display panel 59 receives the light (backlight) from the backlight unit 49 to enhance the display function.
The holding member 25 will now be described with reference to
The holding member 25 includes the first holding member part 26 and the second holding member part 27. The first holding member part 26 is bar-shaped, and has grooves 26D in a direction intersecting (for example, perpendicular to) a direction in which the bar extends. The groove 26D has a groove width W26 and a height T26 to such a degree that the light guide bar 11 is fitted into the groove 26D. Specifically, the groove 26D has substantially the same lengths as the bar width of the light guide bar 11 (a width in the X-direction (direction in which the light guide bars 11 are aligned) intersecting the direction in which the light guide bars 11 extend) and the height of the light guide bar 11 (a width in the Z-direction intersecting the direction in which the light guide bars 11 extend and the direction in which the light guide bars 11 are aligned).
The position of the groove bottom 26Db of the groove 26D (in short, a length from the groove bottom 26Db to the bottom surface 26B of the first holding member part 26) is determined as follows. Specifically, as shown in
As shown in
Specifically, an opening hole 26Dh (a first engagement portion or a second engagement portion) is formed in the groove 26D, and a protrusion 11P (the second engagement portion or the first engagement portion) that fits into the opening hole 26Dh is formed on the light guide bar 11. The opening hole 26Dh (concave fitting portion) and the protrusion 11P (convex fitting portion) described above engage with each other, and thus the light guide bars 11 are prevented from moving with respect to the first holding member part 26 and hence the holding member 25.
As shown in
Consequently, the LEDs 32 and the light guide bars 11 are simultaneously and stably held in the holding member 25 (especially, the grooves 26D) (in short, the holding member 25 covers, with the second holding member part 27, the first holding member part 26 having the grooves 26D, and thus the grooves 26D become hollow, and the LEDs 32 and part of the light guide bars 11 are held within the hollow).
Furthermore, the LED modules MJ are sandwiched between the support stage 21 and the holding member 25, and thus the LED modules MJ are prevented from moving with respect to the holding member 25; the protrusions 11P are fitted into the opening holes 26Dh of the holding member 25, and thus the light guide bars 11 are also prevented from moving with respect to the holding member 25. Hence, the LEDs 32 and the light guide bars 11 are unlikely to be changed in position (in the holding member 25, even if the LEDs 32 and the light guide bars 11 attempt to be moved, since they make contact with the inner wall surfaces of the hollow, variations in position are unlikely to be produced).
For example, even if the light guide bars 11 receive the heat of the LEDs 32 to expand, since the protrusions 11P are fitted into the opening holes 26Dh of the first holding member part 26, the light guide bars 11 do not move with respect to the holding member 25. Hence, the distance between the LED 32 positioned at the end of the hollow of the holding member 25 and the light reception end 12R of the light guide bar 11 is not changed (for example, the separation space between the LED 32 and the light reception end 12R is not changed). Therefore, the light reception end 12R is prevented from moving close to and making contact with the LED 32 due to the heat expansion of the light guide bar 11. By contrast, the light reception end 12R is prevented from being separated from the LED 32, with the result that the rate of entrance of light into the light reception end 12R is not reduced. In other words, the light of the LED 32 reliably enters the light guide bar 11 through the light reception end 12R, and the light guide bar 11 guides the light from the LED 32 without leakage.
Since the light from the LEDs 32 and the light from the light guide bars 11 may be incident on the holding member 25, the holding member 25 is preferably formed of reflective resin (for example, white polycarbonate) (in other words, the holding member 25 can be referred to as a reflector). As shown in
The light guide unit UT will now be described in detail. In the light guide bar group GR of the light guide unit UT, as shown in
Then, the processing portions 13 are not aligned along the X-direction; they are aligned so as to intersect the X-direction (that is, the direction in which the light guide bars 11 are aligned; also referred to as an R-direction). In other words, as shown in
In this way, even if the light reception ends 12R of the light guide unit UT are arranged near the ends that are non-display portions (for example, the perimeter of the liquid crystal display panel 59) in the liquid crystal display panel 59 of the liquid crystal display device 69, the light emission portions 12N for emitting light are placed in the inner side of the panel (for example, close to the vicinity of the center of the display panel) that is the display portion of the liquid crystal display panel 59. Hence, when the light guide unit UT described above is incorporated in the backlight unit 49, and therefore the liquid crystal display device 69, for example, a member for hiding the LEDs 32 is not needed.
Since the member described above is not present, the light of the light guide bars 11 emitted from the light emission portions 12N travels in a desired direction without being blocked, with the result that a loss of the light is not produced. Hence, when the light guide unit UT is incorporated in the backlight unit 49, the efficiency of utilization of the light is enhanced, and furthermore, the backlight unit 49 and therefore the liquid crystal display device 69 and the like are reduced in cost.
Moreover, when the light guide unit UT described above is used, the positions of the light emission portions 12N for emitting light are not close to each other, and they are appropriately arranged in a scattered manner. Hence, the following event is prevented; for example, the light from the light emission portions 12N becomes locally concentrated, the light does not spread to the other areas and planar light including variations in the amount of light is generated (in short, the light of the light guide bars 11 overlaps without being separated, and thus widespread planar light is formed). Therefore, the backlight unit 49 incorporating the light guide unit UT described above supplies high-quality backlight (planar light) to the liquid crystal display panel 59.
Since the light guide unit UT is made larger by further collecting the light guide bar groups GR that are the aggregations of the relatively small light guide bars 11, it is possible to acquire the amount of light suitable for a large backlight unit 49 (in short, by the number of light guide bars 11, the size of the light guide unit UT and the amount of light emitted from the light guide unit UT can be changed).
For example, when one light guide plate is used, a manufacturing mold needs to be changed according to the display area (that is, the display area of the liquid crystal display panel 59) of the liquid crystal display panel 59. However, in the light guide unit UT, since the number of light guide bars 11 or the number of the light guide bar groups GR can be changed without the manufacturing mold being changed, the light guide unit UT can cope with the display area of the liquid crystal display device 69. Hence, although the light guide unit UT is inexpensive, the light guide unit UT can be used for various types.
In the light guide unit UT, since light is not exchanged between the light guide bars 11, it is possible to control the emission of the light on each of the light guide bars 11. In other words, the emission of the light is controlled according to the light guide bars 11 of the light guide unit UT. Hence, the light guide unit UT can be said to be a member suitable for local dimming control (technology for locally controlling the amount of planar backlight).
As shown in
In other words, when a large number of types of light guide bars 11 having different total lengths included in the light guide bar group GR are present, for example, the light reception ends 12R of the light guide bars 11 are only aligned in a row, and thus the positions (that is, the positions of the processing portions 13) for emitting the light from the light guide bars 11 to the outside are prevented from being arranged along the direction in which the light reception ends 12R are aligned, and they are scattered. Hence, the light guide unit UT can simply guide the light in a direction intersecting the direction (X-direction) in which the light reception ends 12R are aligned. The length of the light guide bars 11 can be appropriately changed, and thus it is possible to easily change the distribution of the amount of light in the liquid crystal display panel 59.
Incidentally, as shown in
For example, when the processing portions 13 are formed in two continuous surfaces among the side surface 12S of the bar-shaped light guide bar 11, as shown in
In this way, in light (see white arrows) shown in
Preferably, when, as shown in
As shown in
Moreover, when the distance from the reflective sheet 41 to the light guide bar 11 is longer than the distance from the diffusion plate 43 to the processing portion 13, the optical path of the light from the processing portion 13 is more reliably increased in length. Therefore, the planar light shone on the diffusion plate 43 becomes light that is formed by overlapping the light from a plurality of light guide bars 11 in a widespread area and that has no variations in the amount of light, and thus the quality of the backlight is enhanced.
Preferably, when the surface (light reception surface) of the processing portion 13 faces the reflective sheet 41 and the distance from the reflective sheet 41 to the processing portion 13 of the light guide bar 11 is longer than the distance from the diffusion plate 43 to the processing portion 13, and, as shown in
In short, when the light guide bar 11 is bar-shaped, the processing portion 13 is preferably formed on at least one side surface 12S among the side surfaces 12S of the bar (see
As shown in
In this way, the light traveling from the processing portion 13 passes through the lenses (diffusion lenses) 15 and thus diffuses, and is emitted to the outside. Hence, for example, when the light enters the diffusion plate 43 arranged to cover the lenses 15, the light beam width of the light is increased. Then, the application area of the diffusion plate 43 to which light is applied is increased, a large number of application portions are overlapped and backlight including no variations in the amount of light is generated.
Preferably, in the light guide bar 11 including the lenses 15 described above, as shown in
This is because, even if the light enters parts of the lens surface near the side surfaces 12S sandwiching the top surface 12U, since the curvature of the lenses 15 is low, it is difficult to diffuse the light. In other words, parts of the processing portion 13 close to the side surfaces 12S that easily guide the light toward the parts of the lens surface close to the side surfaces 12S sandwiching the top surface 12U may be omitted. In this way, the cost for processing the processing portion 13 is reduced.
A description has been given of the case where the optical path of the light from the LED 32 is extended as much as possible, thus the degree to which the light is mixed is increased (in short, the light beams as large as possible are overlapped by increasing the length of the optical path and the size of the light beams) and high-quality planar light is generated. However, needless to say, in the backlight unit 49 where the light guide bars 11 are used, as compared with a direct-type backlight unit in which light is made to directly enter the diffusion plate from the LED, it is possible to extend the optical path. Hence, the backlight unit 49 incorporating the light guide unit UT can provide high-quality backlight.
Moreover, although, in the direct-type backlight unit, in order to increase the degree to which the light is mixed, it is necessary to increase the distance from the LED to the diffusion plate, the backlight unit 49 incorporating the light guide unit UT does not need it. Hence, since the distance from the diffusion plate 43 to the processing portion 13 is relatively short, the backlight unit 49 is thin.
Second EmbodimentA second embodiment will be described. Members having the same functions as in the first embodiment are identified with like symbols, and their description will not be repeated.
As shown in the plan view of
Hence, in the light guide bar groups GR facing each other along the Y-direction, the track of light obtained by connecting light from the processing portions 13 (hence, the light emission portions 12N) arranged on the side of the top ends 12T of the individual light guide bars 11 is, as shown in
Then, the light from the backlight unit 49 (that is, the light guide unit UT) has a slight displacement toward the bending point of the broken line; if the degree of the displacement is excessive, the backlight is likely to include variations in the amount of light. Since the track of the light in the shape of the broken line is not parallel to the longitudinal direction and the width direction of the liquid crystal display panel 59, the track is likely to become noticeable as a line of light (variations in the amount of light) due to visual characteristics.
Hence, preferably, as shown in the perspective view of
In this way, since, as shown in
However, in the light guide unit UT described above and shown in
Incidentally, when the light enters the light guide bar 11 through the light reception end 12R, it is desirable to minimize the emission of the light from the light guide bar 11 while the light travels toward the top end 12T (in short, it is desirable to reduce the decrease in the amount of light reaching the processing portion 13). In particular, when, as shown in
In order for this problem to be prevented, an inclination angle (θ°) of the side surface 12S is preferably set such that a relational formula reflecting the critical angle) (θc°) of the material of the light guide bar 11 is satisfied (see
Here, a detailed description will be given with reference to
In general, when the light enters the flat surface of the light reception end 12R, the light does not have a refraction angle equal or more than the critical angle) (θc°) with respect to the flat surface of the light reception end 12R (it is assumed that the light reception point of the light reception end 12R is A point, that one of both ends of the light reception end 12R overlapped by the T-Y plane overlapping the A point is B point and that the other end is C point).
Then, when the light is incident on the side surface 12S including the B point, and the incident point of the side surface is assumed to be D point, an angle ABD, an angle BDA and an angle DAB are determined. Specifically,
angle ABD=90°−θ
angle BDA=θ+θc and
angle DAB=90°−θc.
Then, the incident angle of the light with respect to the side surface 12S including the B point becomes 90°−θ−θc. Preferably, in order for the light not to pass through the side surface 12S including the B point and exit to the outside, at the incident angle (90°−θ−θc) that is greater than the critical angle, total reflection is made to occur. That is, the following relational formula A is derived from 90°−θ−θc≧θc.
θ≦90°−2×θc (Relational formula A)
When the light is incident on the side surface 12S including the C point, and the incident point of the side surface 12S is assumed to be E point, the angle ACE, the angle CEA and the angle EAC are determined. Specifically,
angle ACE=90°+θ
angle CEA=θc−θ and
angle EAC=90°−θc.
The incident angle of the light with respect to the side surface 12S including the C point becomes 90°+θ−θc. The incident angle (90°+θ−θc) is prevented from becoming smaller than the critical angle. Hence, the light with respect to the side surface 12S including the C point is totally reflected.
As shown in
In
For example, when the arrangement distance W of the light guide bar group GR is assumed to be equal to the length L both in the light guide unit UT of
Then, when
θ(r)=tan−1 {(P(r)×m)/L} (Relational formula Ba)
On the other hand, in the light guide unit UT as shown in
θ(u)=tan−1 {(P(u)×m)/L} (Relational formula Bb)
Then, θ(u)<θ(r) is given by the relationship P(u)<P(r). In other words, when, in the light guide unit UT, a predetermined arrangement distance W of the light guide bar group GR and a predetermined length L (the length from the light reception end 12R of the light guide bar 11 having the shortest total length to the top end 12T of the light guide bar 11 having the longest total length) are determined, as shown in
When the inclination angle θ is small as described above, in the process of the light travelling from the light reception end 12R to the top end 12T, the light is unlikely to be emitted from the side surface 12S without reaching the processing portion 13. Consequently, the light guide unit UT as shown in
The following relational formula C can be derived from the relational formula A and the relational formula B.
As is understood from what has been described above, the limit value of the inclination (the inclination angle θ) of the light guide bar 11 is determined depending on the critical angle θc, and furthermore, the arrangement distance P between the light guide bars 11 is determined to achieve such inclination.
Third EmbodimentA third embodiment will be described. Members that have the same functions as in the first and second embodiments are identified with like symbols, and their description will not be repeated.
In the first and second embodiments, the light guide unit UT (see
For example, because of the visual characteristics of a person, the person can hardly sense the decrease in the brightness of the regions other than the center of the liquid crystal display panel 59 (in short, even if the brightness of the peripheral areas of the liquid crystal display panel 59 is somewhat decreased, the liquid crystal display panel 59 is recognized to have an uniform brightness). Then, when the backlight unit 49 emits planar light in which the brightness of the vicinity of the center of the liquid crystal display panel 59 is higher than that of the peripheral areas, the brightness of the liquid crystal display panel 59 is effectively increased (for example, the liquid crystal display device 69 can provide an image of high brightness to the user even if the power consumption is limited).
Hence, for example, as shown in the plan view of
Specifically, in the X-direction that divides two light guide bar groups GR aligned along the Y-direction into two parts, the symmetrical axis ASx is present; in the Y-direction that divides 16 light guide bar groups GR aligned along the X-direction into two parts, the symmetrical axis ASy is present (in short, the light guide bar groups GR (hence, the light guide bars 11) are arranged symmetrically both in a vertical direction and in a lateral direction. In the arrangement of the light guide bar groups GR shown in
In the backlight unit 49 configured as described above, as in
In other words, the bottom of the V-shaped track of the light is close to the symmetrical axis ASy along the Y-direction overlapping the vicinity of the center of the planar light. Consequently, the brightness of the vicinity of the center of the planar light is higher than that of the peripheral areas. Hence, in the backlight unit 49 shown in
Moreover, for example, as shown in the plan view of
In the backlight unit 49 configured as described above, as in
In other words, the straight track of the light is arranged close to the symmetrical axis ASy along the Y-direction overlapping the vicinity of the center of the planar light. Consequently, the brightness of the vicinity of the center of the planar light is higher than that of the peripheral areas. Hence, in the backlight unit 49 shown in
When, as described above, the arrangement of the light guide bars 11 is either a line-symmetrical arrangement or a point-symmetrical arrangement, the characteristic of the brightness distribution of the planar light is also either a line-symmetrical distribution or a point-symmetrical distribution. Hence, the backlight unit 49 including the light guide bars 11 described above is suitable for local dimming control.
Fourth EmbodimentA fourth embodiment will be described. Members that have the same functions as in the first to third embodiments are identified with like symbols, and their description will not be repeated.
The light guide bar 11 that has been described in the first to third embodiments is a rectangular parallelepiped. However, the shape of the light guide bar 11 is not limited to this shape. For example, as shown in
In the light guide bar 11 described above, as shown in
Hence, the light is not emitted from the top end 12T of the light guide bar 11, and easily passes through the top surface 12U and reaches the diffusion plate 43 (in other words, light that is unlikely to enter the diffusion plate 43 is not emitted from the light guide bar 11). Consequently, in the backlight unit 49, a bright spot produced by the light emitted from the top end 12T is reduced, and it is possible to obtain planar light (illumination light) having satisfactory evenness.
There is a light guide bar 11, other than the light guide bar 11 shown in
In the case where, as described above, the light reception side of the processing portions 13 faces the diffusion plate 43, when the two side surfaces 12S where the processing portions 13 are formed are farthest away from the diffusion plate 43 as compared with the other side surfaces 12S, in the optical path of the light (see white arrows) of
For example, as shown in
Since, in the light guide bar 11 described above, as compared with the light guide bar 11 shown in
In the light guide bar 11 shown in
Preferably, in the light guide bar 11 shown in
A fifth embodiment will be described. Members that have the same functions as in the first to fourth embodiments are identified with like symbols, and their description will not be repeated.
In the fourth embodiment, the light guide bar 11 including the straight and tapered light emission portion 12N has been described. However, the shape of the tapered light guide bar 11 is not limited to the straight shape. For example, as shown in
Specifically, the light guide bar 11 is bent, and the processing portion 13 is included in a portion extending from the bent place to the top end 12T. The direction in which the light emission portion 12N including the processing portion 13 extends (in short, the direction from the bent place to the top end 12T) intersects, in the light guide bar group GR, the R-direction in which the light guide bars 11 are aligned and is also perpendicular to the light reception end arrangement line T formed by connecting the positions of the light receiving ends 12R.
Moreover, in the light guide bar group GR, a plurality of linear light emission portions 12N are arranged such that they are perpendicular to the light reception end arrangement line T and are continuous. Hence, the light emission portion arrangement line S formed by connecting the light emission portions 12N is also perpendicular to the light reception end arrangement line T.
In the light guide bar group GR described above, the light emission portion arrangement line S coincides with the direction in which the light emission portions 12N extend. Hence, as shown in
Since, in the backlight unit 49 including the light guide unit UT shown in
A sixth embodiment will be described. Members that have the same functions as in the first to fifth embodiments are identified with like symbols, and their description will not be repeated.
In the light guide unit UT of the first to fifth embodiments, the area of the processing portion 13 of each of the light guide bars 11 is constant. However, the present invention is not limited to this configuration.
For example, as shown in the plan view of
Hence, as shown in a brightness distribution diagram (the brightness distribution diagram showing the relationship between the positions in the Y-direction and the brightness) illustrated next to the plan view of
In this way, because of visual characteristics, for example, the user is unlikely to notice the darkness in the vicinity of the ends along the longitudinal direction of the liquid crystal display panel 59. Hence, when the light guide unit UT described above is incorporated in the liquid crystal display device 69, it is possible to provide a satisfactory image to the user while reducing the power consumption of the LEDs 32.
Since the backlight unit 49 incorporating the light guide unit UT can perform local dimming, it is possible to partially control the amount of light according to an image displayed on the liquid crystal display panel 59. Hence, needless to say, the power consumption is effectively reduced. Since the backlight unit 49 controls the backlight in synchronization with the image displayed on the liquid crystal display panel 59, it is also possible to enhance the moving image display performance of the liquid crystal display device 69.
The present invention is not limited to the embodiments described above; many modifications are possible without departing from the spirit of the present invention.
Although, in the above description, the holding member 25 has a plurality of grooves 26D, the present invention is not limited to this configuration. For example, when the backlight unit 49 incorporates only one light guide bar 11, the holding member 25 has only one groove 26D (in other words, in the above description, since a plurality of light guide bars 11 are used, it is also said that, for ease of handling, the holding members 25 having one groove 26D are continuous).
As shown in the cross-sectional view of
The retaining part 28A is a ring-shaped member that catches the light guide bar 11 and that includes a cut. The support shaft part 28B is a shaft that is continuous to the vicinity of the bottom of the ring-shaped retaining part 28A. The hook part 28C is a member that is hooked on the edge of an opening hole 42H of the backlight chassis 42 and thus the support shaft part 28B (hence, the clip 28) is made to rise from the bottom surface 42B of the backlight chassis 42 (in the reflective sheet 41, a sheet opening hole 41H that covers the opening hole 42H formed in the bottom surface 42B of the backlight chassis 42 is formed, and the hook part 28C is fitted to the opening hole 42H through the sheet opening hole 41H).
Since the clips 28 described above are included in the light guide set ST (set in which the LEDs 32, the light guide bars 11 and the holding member 25 are integral), the light guide bars 11 are more stably fixed to the backlight chassis 42. The position of the clip 28 is not particularly limited; for example, as shown in
For example, as shown in
The manufacturing of the light guide bar group GR including the coupling members 17 is not particularly limited. For example, a mold in which cuts of the shapes of the coupling members 17 are formed is used, and thus integral molding (such as injection molding) may be performed; alternatively, separate light guide bars 11 may be coupled using the coupling members 17 and an adhesive or the like.
As shown in
The clip 28 retains the light guide bar 11 (the light guide bar group GP) that is likely to thermally expand by receiving the heat of the LEDs 32 or the other circuit components. Hence, the clip 28 preferably retains the light guide bar 11 such that the movement of the light guide bar 11 thermally expanding is not prevented. For example, as shown in
Hence, in order for the retaining part 28A to be prevented from making contact along the coupling member 17 that intersects the direction in which the light guide bars 11 extend (see
The type of LED 32 is not particularly limited. For example, as an example of the LED 32, there is an LED that includes a blue light emitting LED chip (a light emitting chip) and a fluorescent member which receives light from the LED chip to emit yellow light (the number of LED chips is not particularly limited). This type of LED 32 generates white light using the light from the blue light emitting LED chip and the light of the fluorescent emission.
However, the fluorescent member incorporated in the LED 32 is not limited to the yellow light emitting fluorescent member. For example, the LED 32 may include a blue light emitting LED chip and a fluorescent member which receives light from the LED chip to emit green light and red light; this LED 32 may generate white light using the blue light from the LED chip and the light (green light/red light) of the fluorescent emission.
The LED chip incorporated in the LED 32 is not limited to the blue light emitting LED chip. For example, the LED 32 may include a red light emitting red LED chip, a blue light emitting blue LED chip and a fluorescent member which receives light from the blue LED chip to emit green light. This is because this type of LED 32 can generate white light using the red light from the red LED chip, the blue light from the blue LED chip and the green light of the fluorescent emission.
The LED 32 containing no fluorescent member may be used. For example, the LED 32 may include a red light emitting red LED chip, a green light emitting green LED chip and a blue light emitting blue LED chip, and may generate white light using the light from all the LED chips.
The light emitted from the individual light guide bars 11 is not limited to white light; red light, green light and blue light may be emitted. The light guide bars 11 that emit red light, green light and blue light are arranged as close to each other as possible to generate white light by the mixing of the light (for example, the light guide bar 11 emitting red light, the light guide bar 11 emitting green light and the light guide bar 11 emitting blue light are arranged adjacent to each other).
Needless to say, embodiments obtained by combining the technologies disclosed above as necessary are also included in the technical scope of the present invention.
LIST OF REFERENCE SYMBOLS
- 21 support stage
- 25 holding member
- 26 first holding member part
- 26D groove
- 26Db groove bottom
- 26Dh opening hole formed in the groove bottom (first engagement portion/second engagement portion)
- 26Ds groove wall
- 27 second holding member part
- 28 clip
- 11 light guide bar (light guide member)
- 11P protrusion formed on the light guide bar (second engagement portion/first engagement portion)
- 12 light propagation portion of the light guide bar
- 12R light reception end of the light guide bar
- 12T top end of the light guide bar
- 12S side surface of the light guide bar
- 12B bottom surface that is one of the side surfaces of the light guide bar
- 12U top surface that is one of the side surfaces of the light guide bar
- T light reception end arrangement line
- 12N light emission portion
- 13 processing portion (optical path change processing portion)
- 13PR triangular prism
- S processing portion arrangement line (light emission portion arrangement line)
- 15 lens
- 17 coupling member
- 17L part member
- 31 mounting substrate
- 31U mounting surface
- 32 LED (light source, light emitting element)
- MJ LED module
- X direction in which the mounting substrates extend
- Y direction in which the mounting substrates are aligned
- Z direction intersecting the X-direction and the Y-direction
- R direction in which the light guide bars are aligned
- 41 reflective sheet
- 41U reflective surface
- 42 backlight chassis (chassis)
- 43 diffusion plate
- 44 prism sheet
- 45 lens sheet
- 49 backlight unit (illumination device)
- 59 liquid crystal display panel (display panel)
- 69 liquid crystal display device (display device)
Claims
1. A light guide set comprising:
- a light source;
- a light guide bar that includes a light reception end receiving light from the light source and that guides the received light; and
- a holding member that holds the light source and a side of the light reception end of the light guide bar,
- wherein, among a first engagement portion and a second engagement portion that engage with each other, one of the engagement portions is formed in the light guide bar, and the other engagement portion is formed in the holding member.
2. The light guide set of claim 1,
- wherein the first engagement portion and the second engagement portion are also fitting portions that fit each other, and one of the engagement portions is convex, and the other engagement portion is so concave as to fit the convex engagement portion.
3. The light guide set of claim 1,
- wherein the holding member has a hollow, and the light source and a part of the light guide bar are held within the hollow.
4. The light guide set of claim 3,
- wherein the first engagement portion and the second engagement portion engage with each other such that the light reception end is separated from the light source placed at an end of the hollow of the holding member.
5. The light guide set of claim 1,
- wherein the holding member is an aggregation of a plurality of holding member parts, and
- the light source and the light guide bar are held in the holding member by being sandwiched between the holding member parts.
6. The light guide set of claim 1, further comprising:
- a clip that retains the light guide bar.
7. The light guide set of claim 6,
- wherein the light guide bar includes: a light propagation portion that propagates the received light by reflecting the received light multiple times therewithin; and a light emission portion that emits the propagated light to an outside, and the clip retains the propagation portion or the light emission portion.
8. The light guide set of claim 1,
- wherein, when a plurality of the light guide bars are provided, the light guide bars are coupled to each other through a coupling member.
9. The light guide set of claim 8, further comprising:
- a clip that retains the coupling member.
10. The light guide set of claim 8,
- wherein a part member along a direction in which the light guide bars extend is connected to the coupling member, and
- the clip catches the part member.
11. The light guide set of claim 1,
- wherein, when a plurality of the light guide bars are provided, the holding members are integrally continuous.
12. An illumination device comprising:
- the light guide set of claim 1; and
- a chassis that holds the light guide set.
13. The illumination device of claim 12, further comprising:
- a diffusion plate that is supported by a surface of the holding member and that receives light from the light guide set; and
- an optical member that is supported by the diffusion plate and that transmits light from the diffusion plate.
14. The illumination device of claim 13,
- wherein the holding member engages with the chassis and the clip also engages with the chassis such that the light guide bar is prevented from moving with respect to the chassis.
15. A display device comprising:
- an illumination device of claim 12; and
- a display panel that receives light from the illumination device.
Type: Application
Filed: Nov 18, 2010
Publication Date: Dec 13, 2012
Applicant: SHARP KABUSHIKI KAISHA (Osaka-shi, Osaka)
Inventor: Takeshi Masuda (Osaka-shi)
Application Number: 13/580,200
International Classification: F21V 8/00 (20060101);